Influence of stripline coupling on the magnetostatic mode line width of an yttrium-iron-garnet sphere

We study the effect of stripline coupling on the damping of magnetostatic modes in an yttrium-iron-garnet sphere. Both the magnetostatic dispersion and line width display a pronounced dependence on the YIG-stripline separation, with the coupling dominating the line width for small separations. By suppressing the coupling effect we use a broadband technique to measure both the Gilbert damping, α = (6.5 ± 0.5) × 10−5, and the inhomogeneous broadening which is mode dependent and as small as 0.075 MHz. Our study therefore reveals the importance of, and a method for, exploring the influence of coupling on damping, which may be useful for future device characterization and design.